pfSense is a free network firewall distribution. pfSense is based on the FreeBSD operating system with a custom kernel and other changes. The pkg_edit.php script which facilitates using the XML-based package settings mechanism does not properly validate the location of the user- specified XML file path given in the "xml" parameter. An attacker with access to the pkg_edit.php page can pass an arbitrary file path to any XML file on the firewall, regardless of path, for inclusion, allowing the XML file to be read regardless of permissions.